How to load scripts into the Text Editor on startup?
Ok, I found a solution for this problem.  Thanks to all for providing answers.  I posed this as a scripting question since I could see no other way of solving my initial problem.  The problem is creating a library of often used scripts that are immediately available every time I open Blender.  This is to emulate Maya's Tool Shelf in which the user can save scripts as buttons in the UI.  

The solution is to open a script in Blender's Text Editor - this creates a text data block for the scene, which is saved with the scene.  Do this on the fresh Default Blender scene to open scripts in the default New Scene, then re-save the scene as Default.
If you want specific scripts available for a specific scene, just open those scripts as data blocks for that scene and save it.

This is not quite a decent solution, since the entire script is saved within the blender file, which could add up to a lot of extra data, plus it exposes the script to unintentional changes.  A better method would be to save each script path in a run_script command as an individual text object.

import bpy


path = "/Users/user_name/Documents/Blender/scripts/modules/script_name.py"
bpy.ops.script.python_file_run(filepath=path)

Then you only save these few lines in the Blender scene file and run it from the Text Editor, and the script is isolated from changes or prying eyes.  It just won't work if the blender file is opened from within a different machine or file system.  Its just a convenient hack until a more elegant UI solution is invented by someone.